In recent years, chargeable/dischargeable lithium-ion secondary batteries (hereinafter referred to simply as batteries as well) have been utilized as driving power supplies for vehicles such as hybrid vehicles, electric vehicles and the like, and portable electronic components such as notebook computers, video camcorders and the like. As such a battery, for example, there is a battery in which a collector body (corresponding to an electrode plate that will be described later) is wound around a winding axis, and a flat plate terminal (corresponding to a collector member that will be described later) is joined to a collector foil laminated region (corresponding to an exposed wound portion that will be described later) of the collector body (the electrode plate) that constitutes an electrode body (corresponding to a flat wound electrode body that will be described later) having a flat oval cross-section (e.g., a battery described in Patent Document 1).
On the other hand, in Patent Document 2, there is disclosed a battery that is designed such that a width (a dimension) W1 of a flat oval cross-section in a major axis direction is larger than a width (a dimension) W2 of plain portions of a positive electrode and a negative electrode (corresponding to electrode plates that will be described later), which constitute a group of electrodes (corresponding to a flat wound electrode body that will be described later) having the flat oval cross-section (W1>W2), in the group of the electrodes (the flat wound electrode body). Specifically, there is described a battery in which in an exposed wound portion that is obtained by winding foil exposed portions of the electrode plates, regions of the exposed wound portion that are located at both ends of the cross-section of the group of the electrodes (the flat wound electrode body) in the major axis direction respectively are lacking, and a region of the exposed wound portion that is located at a center in the major axis direction (corresponding to an exposed wound central portion that will be described later) remains (e.g., FIGS. 2b and 2c described in Patent Document 2).